Fired heaters boilers

Qsupply = E Qfuel + E Qfuel fired heaters boilers... 

Allowing a fired heater, boiler, or furnace to operate with insufficient air is hazardous because... 

An FD system is required, which is one reason this technology has been more popular with boilers than with fired heaters. Boilers are typically FD while fired heaters are typically natural draft. 

Reducing gas is generated from natural gas in a conventional steam reformer. The natural gas is preheated, desulfurized, mixed with steam, further heated, and reformed in catalyst-filled reformer tubes at 760°C. The reformed gas is cooled to 350°C in a waste heat boiler, passed through a shift converter to increase the content, mixed with clean recycled top gas, heated to 830°C in an indirect-fired heater, then injected into reactor 4. 

Fresh waters are, in general, less corrosive towards copper than is sea-water, and copper is widely and satisfactorily used for distributing cold and hot waters in domestic and industrial installations . Copper and copper alloys are used for pipes, hot-water cylinders, fire-back boilers, ball floats, ball valves, taps, fittings, heater sheaths, etc. In condensers and heat exchangers using fresh water for cooling, tubes of 70/30 brass or Admiralty brass are usually used, and corrosion is rarely a problem. 

Joints in copper components may be a source of trouble. Copper/zinc brazing alloys may dezincify and consequently give rise to leaks . In some waters, soft solders are preferentially attacked unless in a proper capillary joint. Copper/phosphorus, copper/silver/phosphorus, and silver brazing alloys are normally satisfactory jointing materials. Excessive corrosion of copper is sometimes produced by condensates containing dissolved oxygen and carbon dioxide. Rather severe corrosion sometimes occurs on the fire side of fire-back boilers and on electric heater element sheaths under scales deposited from hard waters . 

Refractory bricks and cements are needed for equipment operating at high temperatures such as, fired heaters, high-temperature reactors and boilers. 

J. Use of fired heaters the presence of boilers or furnaces, heated by the combustion of fuels, increases the probability of ignition should a leak of flammable material occur from a process unit. The risk involved will depend on the siting of the fired equipment and the flash point of the process material. The factor to apply is determined with reference to Figure 6 in the Dow Guide. 

In such cases, radiant heat transfer is used from the combustion of fuel in a fired heater ox furnace. Sometimes the function is to purely provide heat sometimes the fired heater is also a reactor and provides heat of reaction. The special case of steam generation in a fired heater (a steam boiler) will be dealt with in Chapter 23. Fired heater designs vary according to the function, heating duty, type of fuel and the method of introducing combustion air. However, process furnaces have a number of features in common. A simple design is illustrated in Figure 15.19. The chamber where combustion takes place, the radiant section... 

While this basic definition of cogeneration efficiency seems straightforward, complications are created by the process steam generated from waste heat recovery that can be used for power generation or process heating and that does not require any fuel to be fired in the utility system. The heat supply can be defined as the sum of the heat from fuel (both in the utility boilers and fired heaters) and steam generation from the waste heat recovery (see Figure 23.44)17 ... 

There are distinct differences between Mahoney s and Instone s data (Table 21) concerning fired heaters and boilers. A possible reason for this is that Instone has analysed the process units involved in large losses and Mahoney has analysed the primary causes of large losses. It is known that heaters and boilers are the... 

Examples Boilers Flares Fired heaters Burners Examples Continuous or batch chemical reactions Catalytic cracking Coking... 

Indirect-Fired Equipment (Fired Heaters) Indirect-fired combustion equipment (fired heaters) transfers heat across either a metallic or refractory wall separating the flame and products of combustion from the process stream. Examples are heat exchangers (discussed in Sec. 11), steam boilers, fired heaters, muffle furnaces, and melting pots. Steam boilers have been treated earlier in this section, and a subsequent subsection on industrial furnaces will include muffle furnaces. 

These objectives are equally important in the operation of fired boilers whose principles of operation on the fire-side and flue-gas side are essentially the same as those of process-plant-fired heaters. 

If you try to operate a furnace, fired heater, or boiler with too little combustion air to starve the burners of oxygen to smother or bog down the firebox, then you will likely cause afterburn or secondary combustion in the stack, you will not be able to operate on automatic temperature control, and may even destroy the equipment altogether. 

Some fired heaters, especially boilers, have a device called a purple peeper, which is simply an optical device that looks at a flame. If it does not detect light with a wavelength in the high-frequency (i.e., purple) end of the optical scale, it interprets this as a flame-out. The fuel-gas regulator is automatically shut. 

High-temperature fuel cells are governed by the same gas safety regulations as are fired heaters and boilers, because they, too, operate at above the auto-... 

On boilers Little data is available for fired heaters. 

Combustion calculations show that an oil-fired watertube boiler requires 200,000 lb/h (25.2 kg/s) for air of combustion at maximum load. Select forced- and induced-draft fans for this boiler if the average temperature of the inlet air is 75°F (297 K) and the average temperature of the combustion gas leaving the air heater is 350°F (450 K) with an ambient barometric pressure of 29.9 inHg. Pressure losses on the air-inlet side are, in inFLO air heater, 1.5 air supply ducts, 0.75 boiler windbox, 1.75 burners, 1.25. Draft losses in the boiler and related equipment are, in inH20 furnace pressure, 0.20 boiler, 3.0 superheater, 1.0 economizer, 1.50 air heater, 2.00 uptake ducts and dampers, 1.25. Determine the fan discharge pressure and horsepower input. The boiler burns 18,000 lb/h (2.27 kg/s) of oil at full load. 

Partial oxidation ammonia plants have the same emission sources except for the primary reformer flue gas. The plants have an auxiliary boiler to generate steam for power production and fired heaters, which on account of the sulfur content of the fuel oil release a flue gas containing S02 (< 1500 mg/m3). Other possible emissions are H2S (< 0.3 ppmv), CO (30 ppmv) and traces of dust. The NO, content of the flue gas depends on the configuration of the auxiliary boiler and on the extent electric power generation on the site as opposed to outside supply. The total NO, emission per tonne of product may be somewhat lower than for steam reforming plants. 

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